Field of the Invention
The invention relates to an apparatus for separating printed media, in particular letters or envelopes, which are fed in a stack.
The letters or envelopes may have different thicknesses and permissible formats in an irregular sequence. The processing of letters or envelopes which occur in such a manner is referred to as a mixed-mail operation.
Mail processing systems usually include a mail separating apparatus in which the letters or envelopes are fed successively in a stack, are separated and, if required, are closed, a franking and/or addressing machine with an optional balance, and a depositing apparatus, as is seen in German Utility Model DE-M 96 09 167.3.
The apparatus according to the invention is a component of a letter separating apparatus.
A configuration for pre-separating the printed media is known from German Published, Non-Prosecuted Patent Application DE 196 05 017 A1, in which the letters or envelopes are fed as a stack, vertically one behind another on one edge, and the letters or envelopes are fed laterally away from the stack to a separating apparatus. In that case, the letters or envelopes are disposed between a spring-mounted curved pressure plate and at least one drive roll, as well as a slightly rearwardly inclined guide plate. The standing area for the letters or envelopes and the guide plate are orthogonal to each other.
The drive roll has an external contour with at least one projection which extends over the length of the roll and is parallel to the axis of rotation. The envelope curve of the drive roll projects through an opening in the guide plate to such an extent that at least one projection protrudes from the opening. As a result of the projecting external contour, the stack of letters or envelopes is jogged sufficiently, and the frictional and adhesive forces counteracting the transport are overcome. The force to be introduced is set through the stroke of the drive roll. As a result of the inclination of the guide plate, a stable preferred position of the stack of letters or envelopes is achieved. The axis of the drive roll in that case is parallel to the guide plate. In that case, the problem of separation remains unsolved.
An input device for an appliance for processing sheets, such as paper money or postcards, is also known from German Published, Non-Prosecuted Patent Application DE 27 25 947 A1. That device includes at least one transport belt and at least one backing roller. The backing roller is driven in the opposite direction in relation to the transport belt. The sheets are transported from a sheet stacking point to a sheet processing point through the use of the transport belt. The backing roller is disposed in such a way that there is a gap between the cylindrical outer surface of the roller and the outer surface of the transport belt, which allows at least one of the sheets to pass.
That configuration assumes that the transport belt reaches from the region of the sheet stacking point as far as the region of the sheet processing point. The sheets are transported horizontally on the transport belt and thus sheets are continuously pushed against the backing roller. As a consequence, however, there is additionally a risk that a jam will build up at that point and, as a result, sheets can be damaged, particularly since measures for overcoming the adhesion between the letters are lacking.
The relationships are similar in a document separating apparatus according to European Patent 0 598 571 B1. As a distinction from the solution previously described, belts are used in that case instead of the backing rollers.
Finally, equipment for separating mail items is known from U.S. Pat. No. 4,615,519, in which vertically oriented letters or envelopes are deposited one behind another as a stack of letters or envelopes in a holding area. The stack of letters or envelopes is pressed against a pull-off device through the use of spring force by a thrust element guided on a carrier.
The pull-off device includes a drive roll made of rubber disks disposed at a distance one above another on a shaft. The rubber disks project partly through a guide plate located opposite the holding area and rest on the broad side surface of the front letter or envelope of the stack, with the guide plate engaging like teeth in the gaps between the rubber disks.
Due to the spring force, there is an approximately constant force between the stack of letters and the drive roll. On one hand, viewed alone, that is advantageous. On the other hand, however, it is a problem to introduce a force between the drive roll and the front letter or envelope which overcomes the adhesion and friction between the latter and the rest of the stack and the guide plate, particularly since the adhesive capacity may exhibit very great differences because of different weights, adhesive-surface size and paper finish. Once the drive roll begins to slip, the result is disruption to the automatic operation.
The letters or envelopes which are pulled off pass from the pull-off device to a cylindrical roll and a backing belt located opposite the latter and, following that, to the same combination once more. The drive roll and the two cylindrical rolls are driven jointly by a motor through a toothed belt, which also drives the backing belts through a further toothed belt. The stacked configuration of two separating pairs requires a correspondingly large amount of space and complication.